ItemsControl中Brush、Size、BlurRadius属性绑定失效求助

问题现象 #

通过ItemsControl绑定ObservableCollection<LEDModel>填充StackPanel时，仅Label的ColorString绑定正常显示，Ellipse的Brush、Size以及BlurEffect的BlurRadius绑定完全无效果。无编译/运行时错误，UI树确认StackPanel已正确加载所有项，标签可见。尝试更换Brush类型、数值类型均未解决。

相关代码 #

XAML代码 #

<ItemsControl
    ItemsSource="{Binding ElementName=Control, Path=Leds}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel
                Orientation="Vertical"
                IsItemsHost="True" />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Ellipse
                    Width="{Binding Size}"
                    Height="{Binding Size}"
                    Fill="{Binding Brush}">

                    <Ellipse.Effect>
                        <BlurEffect
                            Radius="{Binding BlurRadius}" />
                    </Ellipse.Effect>
                </Ellipse>

                <Label Content="{Binding ColorString}" />
            </Grid>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

C#代码 #

public partial class LEDStack : UserControl, INotifyPropertyChanged {
    // ...
    public ObservableCollection<LEDModel> Leds { get; }
    // ...
}

public class LEDModel {
    public string ColorString => GetColorString();
    public SolidColorBrush Brush { get; set; } = Brushes.Orange; // 绑定失效
    public double Size { get; set; } = 25d; // 绑定失效
    public double BlurRadius { get; set; } = 10d; // 绑定失效

    private string GetColorString() {
        return $"{Brush.Color.R}, {Brush.Color.G}, {Brush.Color.B}";
    }
}

故障原因及修复方案 #

1. Ellipse被Label遮挡（核心可见性问题） #

Grid中元素按声明顺序堆叠，后声明的Label会完全覆盖先声明的Ellipse，导致Ellipse不可见，误以为绑定失效。

修复：
调整元素顺序，或通过布局属性让Label居中显示在Ellipse上方，避免完全遮挡：

<Grid>
    <Ellipse
        Width="{Binding Size}"
        Height="{Binding Size}"
        Fill="{Binding Brush}">
        <Ellipse.Effect>
            <BlurEffect Radius="{Binding DataContext.BlurRadius, RelativeSource={RelativeSource AncestorType=Grid}}" />
        </Ellipse.Effect>
    </Ellipse>
    <Label Content="{Binding ColorString}" 
           HorizontalAlignment="Center" 
           VerticalAlignment="Center"
           Padding="3"/>
</Grid>

2. BlurEffect的Radius绑定失效 #

BlurEffect不属于FrameworkElement，没有DataContext属性，无法自动继承父元素的DataContext，导致{Binding BlurRadius}找不到数据源。

修复：
通过RelativeSource指定绑定源为父级Grid的DataContext：

<Ellipse.Effect>
    <BlurEffect
        Radius="{Binding DataContext.BlurRadius, RelativeSource={RelativeSource AncestorType=Grid}}" />
</Ellipse.Effect>

或给Grid命名后用ElementName引用：

<Grid x:Name="LedContainer">
    <Ellipse>
        <Ellipse.Effect>
            <BlurEffect Radius="{Binding DataContext.BlurRadius, ElementName=LedContainer}" />
        </Ellipse.Effect>
    </Ellipse>
</Grid>

3. 可选：实现INotifyPropertyChanged支持动态更新 #

当前LEDModel未实现INotifyPropertyChanged接口，仅能显示初始值，后续属性变化无法同步到UI。若需要动态更新LED状态，需补充实现：

using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows.Media;

public class LEDModel : INotifyPropertyChanged
{
    public string ColorString => GetColorString();

    private SolidColorBrush _brush = Brushes.Orange;
    public SolidColorBrush Brush
    {
        get => _brush;
        set
        {
            if (_brush != value)
            {
                _brush = value;
                OnPropertyChanged();
                OnPropertyChanged(nameof(ColorString)); // 同步更新依赖的ColorString
            }
        }
    }

    private double _size = 25d;
    public double Size
    {
        get => _size;
        set
        {
            if (_size != value)
            {
                _size = value;
                OnPropertyChanged();
            }
        }
    }

    private double _blurRadius = 10d;
    public double BlurRadius
    {
        get => _blurRadius;
        set
        {
            if (_blurRadius != value)
            {
                _blurRadius = value;
                OnPropertyChanged();
            }
        }
    }

    private string GetColorString()
    {
        return $"{Brush.Color.R}, {Brush.Color.G}, {Brush.Color.B}";
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

内容的提问来源于stack exchange，提问作者JakobSailer